Premix combustion refers to mixing gas and air in a premix chamber and burning the mixed gas on a burner. The structural design of the burner has a great influence to the combustion situation of the mixed gas. The existing burners, such as an Iron-chrome-aluminum wire mesh burner, are burners with the surface of the support element covered by a wire mesh made of a special material. The flames attach to the surface of the wire mesh, which has a high porosity, good flame stability, a large turndown ratio and a good level of pollutant emission. However, due to the particularity of the wire mesh, the manufacturing technique thereof is complex and the cost thereof is high.
In order to reduce the manufacturing difficulty, some plate type burners produced by simple manufacturing techniques have been developed. For example, the Chinese patent No. 201320092745, entitled “Full premix burner”, and the Chinese patent No. 201310135997, entitled “Positive-pressure-injecting type fully-premixed combustion heating device”, have both proposed a premix burner using a stainless steel plate or a plate with a certain curvature as the substrate. The fire holes thereof are a combination of circular or rectangular holes, the manufacturing thereof is simple, and the cost is low. However, the deficiency thereof lies in that the fire hole flame stability of the simplex circular or rectangular holes is poor. In a case where the gas supply flow is unstable, a flame lift phenomenon is likely to occur, which may further cause resonance of the burner, and thereby may result in damages to the components related to the burner. Furthermore, referring to the patent application No. 201410313365.X, entitled “Gas pre-mixing burner”, it has proposed to provide a main combustion fire hole on a combustion platform higher than the substrate, and expects to achieve the effect of stabilizing the flame through the intersecting between the auxiliary flame of the auxiliary combustion fire hole and the main flame of the main combustion fire hole. However, in this patent application, the main combustion fire hole is higher than the auxiliary combustion fire hole, thus, for small load conditions, a situation may occur where the length of the auxiliary flame is not enough to well intersect the main flame, and at this point the stability of the flame is relatively poor.